Turbomachines rely on turbines to convert fluid energy to mechanical energy. In most configurations, a turbine is connected to a shaft supported by one or more bearings where the shaft rotates along with the turbine as the turbine extracts energy from a fluid stream. For exhaust driven turbines, a shaft may rotate at over 100,000 rpm. Turbomachinery operating at such high rotational speeds generate a significant amount noise.
One type of turbomachinery noise stems lubrication instabilities known as “whirl”. Another type of turbomachinery noise is associated with component clearances and commonly referred to as “rub” (e.g., component-to-component contact). While appropriate choices in lubricant, balancing, and component clearances can minimize noise, no turbomachine operates silently. As described herein, various exemplary arrangements, materials and techniques aim to reduce generation and transmission of turbomachinery noise, especially for turbochargers.